Local Interconnect Network - Overview

Overview

The LIN bus is an inexpensive serial communications protocol, which effectively supports remote application within a car’s network. It is particularly intended for mechatronic nodes in distributed automotive applications, but is equally suited to industrial applications. It is intended to complement the existing CAN network leading to hierarchical networks within cars.

In the late 1990s the Local Interconnect Network (LIN) Consortium was founded by five European automakers, Volcano Automotive Group and Freescale. The first fully implemented version of the new LIN specification was published in November 2002 as LIN version 1.3. In September 2003 version 2.0 was introduced to expand configuration capabilities and make provisions for significant additional diagnostics features and tool interfaces

The protocol’s main features are listed below:

• Single master, up to 16 slaves (i.e. no bus arbitration). This is the value recommended by the LIN Consortium to achieve deterministic time response.
  • Slave Node Position Detection (SNPD) allows node address assignment after power-up
• Single wire communications up to 19.2 kbit/s @ 40 meter bus length.

• Guaranteed latency times.
• Variable length of data frame (2, 4 and 8 byte).
• Configuration flexibility.
• Multi-cast reception with time synchronization, without crystals or ceramic resonators.
• Data checksum and error detection.
• Detection of defective nodes.
• Low cost silicon implementation based on standard UART/SCI hardware.
• Enabler for hierarchical networks.
• Operating voltage of 12 V.

Data is transferred across the bus in fixed form messages of selectable lengths. The master task transmits a header that consists of a break signal followed by synchronization and identifier fields. The slaves respond with a data frame that consists of between 2, 4 and 8 data bytes plus 3 bytes of control information.